Determining the proportion of streamflow that is generated by cold season processes versus summer rainfall in Utah, USA

The proportion of streamflow in the western U.S. that is snowmelt in origin is well-understood to be quite high but has rarely been explicitly quantified. Our data indicate that 98%-99% of streamflow in Utah watersheds originates from melting snow and associated processes. The contribution of summer-month precipitation to annual streamflow in Utah is extraordinarily low: typically 1%-2%. Using soil moisture and well depth data we also demonstrate that vast areas of Utah watersheds are incapable of producing event flow from summer precipitation due to consumptive losses from evapotranspiration and other factors. This analysis is likely representative of areas within other western states that have cool continental climates, abundant snowfall, long-duration snowpacks (meaning that substantial portions of the snowpack do not typically melt during the winter), and sedimentary bedrock.